The present invention relates to a multifunction acoustic device used in a portable instrument such as a portable telephone.
There has been provided an acoustic device of the portable instrument in which a speaker is provided for generating sounds of calling signals, and a vibrating motor is provided for informing the receiver of calling signals without generating sounds. In such a device, since both of the speaker and the motor are mounted in the device, the device is increased in size and weight, and in manufacturing cost.
In recent years, there is provided a multifunction acoustic device in order to remove the above described disadvantages. The multifunction acoustic device comprises a speaker having a vibrating plate and a permanent magnet magnetically connected to a voice coil mounted on the vibrating plate of the speaker. The permanent magnet is independently vibrated at a low frequency of 100-150 Hz so as to inform the receiving of calling signals by the vibration of the case of the device, which is transmitted to the body of the user of the device.
FIG. 7 is a sectional view of a conventional electromagnetic induction converter disclosed in Japanese Patent Laid Open 5-85192. The converter comprises a diaphragm 606 mounted in a case 612 at a periphery thereof, a voice coil 609 secured to the underside of a central portion 607 of the diaphragm 606, a spring plate 611 mounted in the case 612, and a permanent magnet 610 secured to a central portion of the spring plate 611, inserted in the voice coil 609.
By applying a low or high frequency signal to the voice coil 609, the spring plate 611 is vibrated in the polarity direction Y of the magnet 610.
In the device, the diaphragm 606 and the spring plate 611 are relatively moved through the magnetic combination between the voice coil 609 and the magnet 610. Consequently, when a low frequency signal or a high frequency signal is applied to the voice coil 609, both of the diaphragm 606 and the spring plate 611 are sequentially vibrated. As a result, sounds such as voice, music and others generated from the device are distorted, thereby reducing the quality of the sound. In addition, vibrating both of the voice coil 609 and the magnet 610 causes the low frequency vibration of the magnet to superimpose on the magnetic combination of the voice coil 609 and the magnet 610, which further largely distorts the sounds.
FIG. 8 is a sectional view showing a conventional multifunction acoustic device. The device comprises a speaker vibrating plate 703 made of plastic and having a corrugated periphery 703a and a central dome, a voice coil 704 secured to the underside of the vibrating plate 703 at a central portion, and a magnet composition 710. The vibrating plate 703 is secured to a frame 709 with adhesives.
The magnetic composition 710 comprises a lower yoke 705, a core 701 formed on the yoke 705 at a central portion thereof, an annular permanent magnet 702 mounted on the lower yoke 705, and an annular upper yoke 706 mounted on the permanent magnet 702. The lower yoke 705 and the upper yoke 706 are resiliently supported in the frame 709 by spring plates 707 and 708. A magnetic gap 711 is formed between a periphery 701a of the core 701 and an inside wall 706a of the upper yoke 706 to be magnetically connected to the voice coil 704.
When an alternating voltage is applied to the voice coil 704 through input terminals 712a and 712b, the speaker vibrating plate 703 is vibrated in the direction Y to generate sounds at a frequency between 700 Hz and 5 KHz. If a low frequency signal or a high frequency signal is applied to the voice coil 704, the speaker vibrating plate 703 and the magnetic composition 710 are sequentially vibrated, since the magnetic composition 710 and the speaker vibrating plate 703 are relatively moved through the magnetic combination of the voice coil 704 and the magnet composition 710.
As a result, sounds such as voice, music and others generated from the device are distorted, thereby reducing the quality of the sound. In addition, the driving of both the voice coil 704 and the magnetic composition 710 causes the low frequency vibration to superimpose on the magnetic combination of the voice coil 704 and the magnetic composition 710, which further largely distorts the sounds.
FIG. 9 is a sectional view showing another conventional multifunction acoustic device. The device comprises the speaker vibrating plate 703 made of plastic and having the corrugated periphery 703a and the central dome, the voice coil 704 secured to the underside of the vibrating plate 703 at a central portion, and the magnet composition 710. The vibrating plate 703 is secured to the frame 709 with adhesives.
The magnetic composition 710 comprises a lower yoke 803, core 701 formed on the yoke 803 at a central portion thereof, an annular permanent magnet 802 secured to the lower yoke 803, and annular upper yoke 706 having a peripheral wall 706b and mounted on the permanent magnet 702. The upper yoke 706 is resiliently supported in the frame 709 by spring plates 807 and 808. A first magnetic gap 801 is formed between a periphery 701a of the core 701 and an inside wall 706a of the upper yoke 706 to be magnetically connected to the voice coil 704. A second gap 805 is formed between a periphery 803a of the lower yoke 803 and inside wall 706a of the upper yoke 706. A driving coil 806 is secured to the frame and inserted in the second gap 805.
When an alternating voltage is applied to the voice coil 704 through input terminals 712a and 712b, the speaker vibrating plate 703 is vibrated in the direction Y to generate sounds at a frequency between 700 Hz and 5 KHz. If a low frequency signal or a high frequency signal is applied to the voice coil 704, the speaker vibrating plate 703 and the magnetic composition 710 are sequentially vibrated, since the magnetic composition 710 and the speaker vibrating plate 703 are relatively moved through the magnetic combination of the voice coil 704 and the magnet composition 710.
When a high frequency signal for music is applied to the voice coil 704, only the speaker vibrating plate 703 is vibrated. Therefore, there does not occur distortion of the sound. Furthermore, when a low frequency signal is applied to the driving coil 806, only the magnetic composition 710 is vibrated, and the speaker vibrating plate 703 is not vibrated.
However if a high frequency signal is applied to input terminals 712a, 712b, and a low frequency signal is also applied to input terminals 804a, 804b, the speaker vibrating plate 703 and magnetic composition 710 are sequentially vibrated, thereby reducing the sound quality.
In the above described conventional devices, both the speaker vibration plate and the magnetic composition are vibrated when a low frequency signal or a high frequency signal is applied to the voice coil. This is caused by the reason that the low frequency vibrating composition is vibrated in the same direction as the high frequency vibrating direction.
An object of the present invention is to provide a multifunction acoustic device in which a vibrating member is not vibrated together with another vibrating member, thereby removing disadvantages of conventional devices.
According to the present invention, there is provided a multifunction acoustic device comprising a frame, a speaker vibrating plate supported in the frame, a voice coil secured to the speaker vibrating plate, a rotor having magnetic poles and rotatably supported in the frame, a stator having magnetic poles and provided in the frame, corresponding to the rotor, a first permanent magnet provided on the rotor, at least one coil for forming magnetic fluxes between the magnetic poles of the rotor and the magnetic poles of the stator.
The device further comprises eccentric means provided on the rotor for vibrating the rotor during the rotation of the rotor.
The first permanent magnet is an annular magnet, and the voice coil is disposed in a gap formed in the annular magnet.
In an aspect of the invention, the coil is disposed in the stator.
A second permanent magnet is provided in the gap for increasing a magnetic flux density in the gap.
The eccentric means is a weight eccentrically provided in the rotor.
The device further comprises a driving circuit for energizing the coil in the stator for rotating the rotor.
In a further aspect of the invention, the rotor comprises a lower rotor yoke rotatably mounted in the frame, and an upper rotor yoke secured to the lower rotor yoke, and the stator comprises a lower stator yoke and an upper stator yoke secured to the lower stator yoke.
The first permanent magnet is disposed between the lower rotor yoke and the upper rotor yoke, and the stator coil is disposed between the lower stator yoke and the upper stator yoke, and the rotor and the stator are formed into a synchronous motor.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.